This patent application relates to lead-acid batteries, particularly to the structural integrity of lead-acid batteries subject to varying operating conditions and electrical loads.
The internal plates of lead-acid batteries which are usually grids, expand with time, temperature, and load conditions. Grid expansion is more significant with the positive plate, which results from corrosion which adheres to the cell grids as a result of the electrochemical reaction of the battery contents. Grid expansion is particularly problematic in sealed lead-acid batteries due to the hazardous chemical materials housed within the battery case. Often times, as internal grids expand the corresponding pressure of the expansion causes the battery case to fracture or crack. This problem is particularly pronounced in the area of the case cover surrounding the positive battery terminal, due to greater expansion of the positive grid.
Presently, several battery terminals and case arrangements are known utilizing a variety of sealing configurations designed to permit movement of the positive terminal relative to the case at the positive grid grows. The seal between the battery and terminal has been maintained in the course of relative movement by use of variety of bushings, O-rings, or gaskets between the case and the terminal structures. However such sealing components can deteriorate and fail over time or with excessive pressure deformation.
Therefore, a unitary expandable case sealed to the battery terminal seal is provided for relieving internal grid growth pressure on the seal at the terminal and maintaining battery/terminal seal integrity.